This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Investigation of Urea Derived Deposits Composition in SCR Systems and Their Potential Effect on Overall PM Emissions
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 05, 2016 by SAE International in United States
Annotation ability available
Ideally, complete thermal decomposition of urea should produce only two products in active Selective Catalytic Reduction (SCR) systems: ammonia and carbon dioxide. In reality, urea thermal decomposition reaction includes the formation of isocyanic acid as an intermediate product. Being highly reactive, isocyanic acid can initiate the formation of larger molecular weight compounds such as cyanuric acid, biuret, melamine, ammeline, ammelide, and dicyandimide [1,2,3,4]. These compounds can be responsible for the formation of deposits on the walls of the decomposition reactor in urea SCR systems. Composition of these deposits varies with temperature exposure, and under certain conditions, can create oligomers such as melam, melem, and melon [5, 6] that are difficult to remove from exhaust systems. Deposits can affect the efficiency of the urea decomposition, and if large enough, can inhibit the exhaust flow. These deposits could also increase downstream Particulate Matter (PM) emissions, which could lead to an engine exceeding the regulated emission standards.
This paper presents a suitable analytical method adapted for quantification of urea and by-products of urea thermal decomposition. This method was able to quantify seven major urea-related soluble monomers, as well as fully dissociated insoluble oligomers to monomers.
Urea-related composition of deposits, including oligomers collected from a urea decomposition reactor under various exhaust conditions, are compared in the paper.
The paper also presents composition results of urea and urea-related by-products on PM filters collected downstream of the aftertreatment system of an off-road engine during certification test cycles.
|Technical Paper||Simultaneous Reduction of HC, NO x and PM by Using Active Regeneration Technique|
|Technical Paper||Robust SCR Design Against Environmental Impacts|
CitationEakle, S., Kroll, S., Yau, A., Gomez, J. et al., "Investigation of Urea Derived Deposits Composition in SCR Systems and Their Potential Effect on Overall PM Emissions," SAE Technical Paper 2016-01-0989, 2016, https://doi.org/10.4271/2016-01-0989.
- Bernhard , A. et. al. Hydrolysis and Thermolysis of Urea and its Decomposition Byproducts Biuret, Cyanuric Acid, and Melamine Over Anatase TiO 2 Applied Catalysis B: Environmental 115-116 2012 129 137
- Way , P. , Viswanathan , K. , Preethi , P. , Gilb , A. et al. SCR Performance Optimization Through Advancements in Aftertreatment Packaging SAE Technical Paper 2009-01-0633 2009 10.4271/2009-01-0633
- Schaber , P. et. al. Thermal Decompostion (Pyrolysis) of Urea in an Open Reaction Vessel Thermochimica Acta 424 2004 131 142
- Abidin , Z. , Das , K. , and Roberts , C. 3D-Semi 1D Coupling for a Complete Simulation of an SCR System SAE Technical Paper 2013-01-1575 2013 10.4271/2013-01-1575
- Redemann C. E. and Lucas H. J. Some Derivatives of Cyameluric Acid and Probable Strructes of Melam, Melem, and Melon J. Am. Chem. Soc. 62 4 1940 842 846 10.1021/ja01861a038
- Jürgens , B. et. al. Melem (2,5,8-Triamino-tri-s-triazine), an Important Intermediate during Condensation of Melamine Rings to Graphitic Carbon Nitride: Synthesis, Structure Determination by X-ray Powder Diffractometry, Solid-State NMR, and Theoretical Studies J. Am. Chem. Soc. 125 34 2003 10288 10300 10.1021/ja0357689
- Yassine , M. et. al. Development of a Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry Method For Detection And Quantification Of Urea Thermal Decomposition By-Products in Emission From Diesel Engine Employing Selective Catalytic Reduction Technology Journal of Chromatography A 1229 2012 208 215
- Weeks , C. , Ibeling , D. , Han , S. , Ludwig , L. et al. Analytical Investigation of Urea Deposits in SCR System SAE Int. J. Engines 8 3 1219 1239 2015 10.4271/2015-01-1037